Issued 4 July 2007
Another drier than average month in rainfall deficient areas
With the notable exceptions of Gippsland and southeast Queensland, June rainfall was mainly below to very much below average in the rainfall deficient areas of southwest WA, southern and southeastern Australia. Heavy to flood rains removed rainfall deficits in Gippsland, while above to very much above average falls provided some relief in southeast Queensland.
12-month rainfall deficiencies
For the 12-month period from July 2006 to June 2007, there were serious to severe rainfall deficiencies over southern and eastern Australia in an arc extending across southeastern SA, southwest, south-central and northeast Victoria, and the tablelands and western slopes in southeastern NSW. A large part of southeast Queensland was also affected, as were northern and eastern Tasmania, and WA west of a line from Dampier in the north to Bremer Bay in the south.
Record low falls for this particular 12-month period were recorded near Albury-Wodonga, around Melbourne, in parts of northern Tasmania, in the far southeast of SA and along WA’s west coast between Shark Bay and Geraldton. Deficiencies are less extensive than they were for the twelve months to May, mostly because June 2006 was much drier than June 2007.
The worst of the long-term deficiencies are likely to remain for some time. For them to be removed by the end of September, for example, falls over the next three months would need to be in the highest 10% of the historical record in some areas, especially in Victoria and WA.
The deficiencies discussed above have occurred against a backdrop of multi-year rainfall deficits that have severely stressed water supplies in the east and southwest of the country.
An important consideration in the recovery from drought is the different rate at which systems respond to rainfall deficiencies. At the current time, many catchments in eastern Australia are excessively dry from a very protracted period of below average rainfall and above average temperatures. This means that it will take above average rainfall just to produce average runoff, and very considerable rainfall to make a material difference to water storages.
Lowest on record - lowest in the historical analysis, which runs from 1900.
Severe deficiency - rainfalls in the lowest 5% of historical totals.
Serious deficiency - rainfalls in the lowest 10% of historical totals, but not in the lowest 5%.
Very much below average - rainfalls in the lowest 10% of historical totals.
Below average - rainfalls in the lowest 30% of historical totals, but not in the lowest 10%.
Average - rainfalls in the middle 40% of historical totals.
Above average - rainfalls in the highest 30% of historical totals, but not in the highest 10%.
Very much above average - rainfalls in the highest 10% of historical totals.
Product Code IDCKGD0AR0